Activity-guided isolation of constituents of Renealmia nicolaioides with the potential to induce the phase II enzyme quinone reductase

Three new prenylated dihydrochalcones, (+/-)-nicolaioidesins A, B, and C (1-3), as well as a new natural product, 5-styrylfuran-2-carboxylic acid methyl ester (4), along with four known compounds, 2'-hydroxy-4',6'-dimethoxychalcone (5), (+/-)-5-hydroxy-7-methoxyflavanone (6), (+/-)-5-hydroxy-7,4'-dimethuxyflavanone, and panduratin A, were isolated from the roots of Renealmia nicolaioides, using a bioassay to determine the induction of quinone reductase (QR) activity with cultured Hepa 1c1c7 mouse hepatoma cells. Among these isolates, 5 and 6 induced QR activity, with observed concentrations to double activity (CD) values of 1.7 and 0.9 mug/mL, respectively, while the other constituents were not regarded as being active (CD >10 mug/mL). The chemical structures of 1-4 were elucidated by spectroscopic methods. A biogenetic pathway for the formation of (+/-)-nicolaioidins A-C (1-3) is proposed.